Possibly the largest land mammal of all time, rivaled only by Palaeoloxodon namadicus, the Asian straight-tusked elephant. Unlike modern rhinos, he prefers leaves to grass, since grass was not abundant yet.

On a more important note: PLEASE. STOP. KILLING. RHINOS. Rhino horns are no more than incredibly compressed hair (They are composed solely of keratin, the protein that forms hair, nails, claws, and tetrapod scales.) and will not cure any diseases, extend your life expectancy, nor boost your sex life.